Cope holder device

ABSTRACT

An upper die supporting section for supporting an upper die is provided to a lower portion of a holder body  7 , a pressing section for pressing the upper die against the upper die supporting section is provided to a lower portion of an upper die clamp  11  supported to the holder body  7  in a rocking manner with a vicinity of a center in a vertical direction being as a supporting point. A locking member which freely locks into a drop-proof groove provided to the upper die is provided to a lower portion of the upper die clamp  11 , and it is biased towards the upper die supporting section. Clamping force applying means  13  for pressing an upper portion of the upper die clamp  11  so as to apply a clamping force for clamping the upper die using the upper die clamp  11  is provided. A pressure receiving member  59  which is pressed by the clamping force applying means  13  is provided to the upper portion of the upper die clamp  11  so that its advancing and retreating are freely adjusted and an opening quantity of the upper die clamp  11  at the time of unclamping is freely selected from a plurality of stages.

TECHNICAL FIELD

[0001] The present invention relates to upper die holder apparatus in apress brake, and more specifically relates to the upper die holderapparatus which is capable of easily attaching/detaching an upper dieto/from an upper table in the press brake so as to replace it.

BACKGROUND ART

[0002] Conventionally, press brakes are constituted so that an uppertable (occasionally called as an upper apron) and a lower table(occasionally called as a lower apron) are opposed to each other in avertical direction, and suitable one of the upper table and the lowertable is driven up and down as a ram.

[0003] In the press brakes having the above constitution, in order tobend a plate shaped workpiece, a lower die (die) is attached to an upperportion of the lower table and an upper die (punch) is attached to alower portion of the upper table.

[0004] In the above constitution, after a workpiece is located on thelower die, the upper die is engaged with the lower die so that theworkpiece can be bent.

[0005] Incidentally, in press brakes, in order to replace the upper dieaccording to a difference in bending forms or the like of workpieces,for example, many upper die holder apparatuses are attached to the lowerportion of the upper table, and these upper die holder apparatusessupport the upper die to the upper table so that the upper die can bedetached and replaced.

[0006] With reference to FIGS. 1 and 2, a prior upper die holderapparatus 101 is provided with a holder body 105 which is attached to anupper table 103 detachably, an upper die supporting section 109 forsupporting an upper die 107 is provided so as to be integral with alower portion of the holder body 105, and an upper die clamp 111 whichfreely presses and fixes an upper portion of the upper die 107 to theholder supporting section 109 is supported to the holder body 105 in arocking manner with a vicinity of an approximately center in a verticaldirection being as a supporting point.

[0007] Further, a pressing member 113 for pressing the upper die 107against the upper die supporting section 109 is provided to a lowerportion of the upper die clamp 111, a wedge piece 115 (locking member)which freely locks into a drop-proof groove 107G provided to the upperdie 107 is provided below the pressing member 113 so as to freelyadvance and retreat, and is biased to a direction of the upper diesupporting section 109 by a resilient member 117. An inclined plane 115Sis formed on an upper surface of a tip of the wedge piece 115 so as tobe easily engaged with and detached from the drop-proof groove 107G. Thewedge piece 115 is composed of a plurality of wedge piece dividingpieces.

[0008] Further, a clamping force applying means 119 for pressing theupper portion of the upper die clamp 111 so as to apply a clamping forcefor clamping the upper die 107 via the upper die clamp 111 is providedto the holder body 105.

[0009] The clamping force applying means 119 is included in a cylinder121 of a front-rear direction provided to the holder body 105, and twopistons l23 are provided slidably in the cylinder 121 in the front-reardirection. Pin-shaped pusher sections 125 are projected respectivelyfrom the pistons 123 towards the outside, and the pusher sections 125are projected outward. Tips of the pusher sections 125 can touch andseparate from a pressing screw 127 as a pressure receiving sectionprovided to the upper portion of the upper die clamp 111.

[0010] Further, a resilient member 129 such as a coil spring for alwaysbiasing the piston 123 so as to always press the piston 123 inward iswound around the pusher sections 125 of the pistons 123. Moreover, anoil passage 131 which communicatively connects to an inside of thecylinder 121 is formed on the holder body 105, and the oil passage 131is communicatively connected with a pressure oil supply source (notshown) via a hydraulic hose 133.

[0011] In addition, an adapter plate 135 having a divergent notchedportion on its lower center is mounted integrally to a front surface ofthe holder body 105. The adapter plate 135 touches a front lower portionof the upper table 103, and a clamp jaw 139 is clamped by a clampingbolt 137 screwed up to the upper table 103 so that the adapter plate 135is pressed and fixed to the upper table 103. As a result, the holderbody 105 is mounted to the upper table 103.

[0012] In order to adjust a vertical position (height position) of theholder body 105, a wedge member 141 lies between an upper surface of theholder body 105 and a lower surface of the upper table 103 so that itsposition is freely adjusted to a horizontal direction, and a fixing bolt145 which pierces a slot 143 in the horizontal direction provided on theadapter plate 135 is screwed up into the wedge member 141.

[0013] In the prior constitution, therefore, when upper die 107 isdetached from the upper table 103 so as to be replaced, the pushersections 125 of the pistons 123 in the cylinder 121 are retreated sothat the upper die clamp 111 is in an unclamped state. The wedge piece115 (a plurality of wedge piece dividing pieces) which is biased by theresilient member 117 is hooked on the drop-proof groove 107G of theupper die 107 so that the in upper die 107 it held. When the upper die107 is front-removed the upper die 107 is twisted so that the wedgepiece 115 is retreated against the biasing force of the resilient member117 and the upper die 107 is removed.

[0014] Further, at the time of attaching, namely, first-feeding theupper die 107, when the upper die 107 is inserted between the upper diesupporting section 109 of the holder body 105 and the upper die clamp111 from a lower side, the wedge piece 115 is retreated against thebiasing force of the resilient member 117 and then is advanced again bythe resilient member 117 so as to be hooked onto the drop-proof groove107G of the upper die 107 and the upper die 107 is held.

[0015] At the time of replacing the upper die 107, however, when astronger force than the biasing force of the resilient member 117 isapplied to the upper die 107 in such a manner that the upper die 107 isslid mightily or a twisting force is suddenly applied to the die, thereis a danger such that the upper die 107 drops even when it is notfront-fed and front-removed.

[0016] The present invention is devised in order to solve the aboveproblem, and an object of the invention is to provide an upper dieholder apparatus which is capable of easily detaching an upper die froma press brake and replacing it, and moving the upper die to a horizontaldirection without a danger such that the upper die drops particularlywhen the upper die is not front-fed and front-removed.

DISCLOSURE OF THE INVENTION

[0017] In order to achieve the above object, an upper die holderapparatus of the present invention based on a first aspect includes: aholder body; an upper die supporting section provided to a lower portionof the holder body, the upper die supporting section for supporting anupper die; an upper die clamp supported to the holder body in a rockingmanner, the upper die clamp being supported in a rocking manner with avicinity of a center in a vertical direction of the holder body being asa supporting point; a pressing member provided to a lower portion of theupper die clamp, the pressing member for pressing the upper die againstthe upper die supporting section; a locking member provided to a lowerportion of the upper die clamp, the locking member being biased towardsthe upper die supporting section so as to freely lock into a drop-proofgroove provided to the upper die; clamping force applying means providedto the holder body, the clamping force applying means pressing an upperportion of the upper die clamp so that the upper die clamp clamps theupper die: and a pressure receiving member provided to an upper portionof the upper die clamp, the pressure receiving member having a pressuresensing surface to be pressed by the clamping force applying means. Inthe above constitution, the pressure receiving member is provided sothat its advancing and retreating are adjusted to a pressing directionby the clamping force applying means, and the pressure receiving memberis provided so that an opening quantity of the upper die clamp at thetime of unclamping is freely selected between a plurality of stages.

[0018] Therefore, since the a position of the pressure sensing surfaceof the pressure receiving member can be selected from a plurality ofstages, the opening quantity of the upper die clamp at the time ofunclamping can be switched between a plurality of stages by a simpleoperation. When the upper die is not front-fed and front-removed, forexample, the opening quantity is set to be small, so that the upper diecan be moved to a lateral direction without a danger such that ofdropping. When the opening quantity is set to large, suitable one ofboth left and right sides of the upper die is inclined downward, theupper die is pushed easily against the biasing force of the lockingmember and simultaneously the upper die is front-fed and front-removedeasily.

[0019] In an upper die holder apparatus of the present invention basedon a second aspect depending from the upper die holder apparatus basedon the first aspect, the opening quantity of the upper die clamp at thetime of unclamping is adjustable so that a locked state between thelocking member and the drop-proof groove of the upper die is freelyselected from a first stage where the upper die cannot be drawn downwardand a second stage where the upper die can be drawn downward.

[0020] Therefore, when the upper die is not front-fed and front-removed,therefore, the opening quantity is set to the first stage so that theupper die can be moved to a lateral direction without a danger ofdropping. When the opening quantity is set to the second stage, theupper die is easily front-fed and front-removed.

[0021] In an upper die holder apparatus of the present invention basedon a third aspect depending from the upper die holder apparatus based onthe first or second aspect, the pressure receiving member is screwedinto the upper portion of the upper die clamp, and a position leverwhich is rotated so as to advance and retreat the pressure receivingmember gradationally is provided to the pressure receiving member.

[0022] Therefore, since a position of the pressure sensing surface ofthe pressure receiving member is switched gradually between the pluralstages only by a simple operation for rotating the position lever, theopening quantity of the upper die clamp at the time of unclamping iseasily switched between the plural stages.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1 is a sectional view of FIG. 2 illustrating a prior example:a left side with respect to a center line illustrates a state that anupper die clamp is opened: and a right side illustrates a state that theupper die clamp clamps an upper die.

[0024]FIG. 2 is a front view of an upper die holder apparatus accordingto a prior example.

[0025]FIG. 3 is a partially sectional view of a mode of the presentinvention illustrating a first-stage switching state by means of aposition lever when the upper die clamp is in an unclamped state.

[0026]FIG. 4 is a partially sectional view of the mode of the presentinvention illustrating a second-stage switching state by means of theposition lever when the upper die clamp is in the unclamped state.

[0027]FIG. 5 shows the mode of the present invention: a right side withrespect to an extended line of a center line drawn on an upper part is asectional view taken in the direction of the arrow along the line V-V inFIG. 6 that illustrate a state that the upper die clamp clamps the upperdie; and a left side with respect to the extended line of the centerline is a sectional view taken in the direction of the arrow along theline V′-V in FIG. 6 that illustrates a state that the upper die clamp isopened.

[0028]FIG. 6 is a front view of the upper die holder apparatusillustrating the mode of the present invention.

[0029]FIG. 7 is a sectional view taken in the direction of the arrowalong the line VII-VII in FIG. 3.

[0030]FIG. 8 is a partially sectional view of a lower portion of theupper die clamp.

THE BEST MODE FOR CARRYING OUT THE INVENTION

[0031] Modes of an upper die holder apparatus and a method of removingan upper die from the upper die holder apparatus according to thepresent invention are explained below with reference to the drawings.

[0032] With reference to FIGS. 5 and 6, an upper die holder apparatus 1of this mode is attached detachably to a lower portion of an upper table3 in a press brake (an entire constitution is not shown). Many upper dieholder apparatuses 1 are attached to the lower portion of the uppertable 3 in a horizontal direction with suitable intervals.

[0033] That is to say, an upper die 5 in the press brake is composed ofone upper die which is long in a horizontal direction (in FIG. 5, adirection vertical to a sheet surface, and in FIG. 6, the horizontaldirection), or a plurality of divided type upper dies having differentlengths which are suitably combined to be used. In order to cope withboth the cases, the many upper die holder apparatuses 1 are attached tothe upper table 3 with suitable intervals.

[0034] As is clear from FIG. 5, the upper die holder apparatus 1 isconstituted so as to include a holder body 7 which is detachablyattached to the upper table 3, an upper die clamp 11 which freelypresses and fixes an upper portion 5U of the upper die 5 to an upper diesupporting section 9 provided integrally with a lower portion of theholder body 7, clamping force applying means 13 for applying a clampingforce to the upper die clamp 11, clamp switching means 15 for freelytransmitting and removing the clamping force by the clamping forceapplying means 13 to/from the upper die clamp 11, upper die clampholding means 17 for holding the upper die clamp 11 to a lower portionof the holder body 7 in a rocking manner, and releasing state holdingmeans 19 (see FIG. 6) for freely holding the upper die clamp 11 in astate that the clamp of the upper die 5 is released.

[0035] More specifically, the holder body 7 has the upper die supportingsection 9 with thin thickness which is integral with a lower portion ofa block section 7B which is thick in a front-rear direction. An adapterplate 25 which projects upward is attached integrally to a front surface(in FIG. 5, a left surface) of the block section 7B of the holder body 7by a plurality of bolts 21 and pins 23 (see FIG. 6).

[0036] The adapter plate 25 has, as shown in FIG. 6, a divergent notchedportion on its lower center. As shown in FIG. 5, a rear surface of theupward projected portion of the adapter plate 25 touches a front lowerportion of the upper table 3, a clamp jaw 29 is clamped by a clampingbolt 27 screwed up into the upper table 3, and the upward projectedportion of the adapter plate 25 is pressed and fixed to the upper table3, so that the holder body 7 can be attached to the upper table 3.

[0037] A locking section 31 projects from a rear surface of a lowerportion of the clamp jaw 29, and a hooking section 33 which can behooked on the locking section 31 projects from a front surface of theupward projected portion of the adapter plate 25. When the holder body 7is attached, therefore, even if the clamping bolt 27 is loosened, thehooking section 33 of the adapter plate 25 is engaged with the lockingsection 31 of the clamp jaw 29, thereby preventing the adapter plate 25from dropping.

[0038] In order to adjust a vertical position (height position) of theholder body 7, a wedge member 35 lies between an upper surface of theholder body 7 and a lower surface of the upper table 3 so that itsposition is freely adjusted to the horizontal direction in FIG. 5, and afixing bolt 39 which pierces an insertion hole 37 provided on theadapter plate 25 is screwed into the wedge member 35.

[0039] In the above constitution, the clamp jaw 29 is maintained to beclamped loosely so that the holder body 7 does not drop, and the thewedge member 35 is adjusted to the horizontal direction in FIG. 5 in astate that the fixing bolt 39 is loosened, thereby finely adjusting theholder body 7 up and down with respect to the upper table 3.

[0040] The upper die clamp 11 is composed of a plate shaped memberhaving approximately same width as a width of the holder body 7 in thehorizontal direction, and a corresponding upward projected portion isformed on a portion of the adapter plate 25 corresponding to thedivergent notched portion. In order to press and fix the upper section5U of the upper die 5 between the upper die supporting section 9 and theupper die clamp 11, the upper die 5 is supported to the holder body 7 bythe upper die clamp holding means 17 in a rocking manner.

[0041] More specifically, in the upper die clamp holding means 17, aplurality of through holes 11H are provided on a vicinity of a center ofthe upper die clamp 11 in the vertical direction, a mounting bolt 41pierces the through holes 11H and is screwed up and fixed to a left sideof the upper die supporting section 9 horizontally in FIG. 5, and a coilspring 43, which biases the upper die clamp 11 to a direction where theupper die clamp 11 is always pressed, is set resiliently so that theupper die clamp 11 is held on a head portion of the mounting bolt 41. Asa result, the upper die clamp 11 is supported in the rocking manner.

[0042] Further, a mounting nut 45 which pierces the through holes 11 onthe upper die clamp 11 on a right side in FIG. 5 is screwed up and fixedto a screw portion of the mounting bolt 41 which projects horizontallyto the right side of the upper die supporting section 9 in FIG. 5, andthe coil spring 43, which biases the upper die clamp 11 to a directionwhere the upper die clamp 11 is always pressed, is set resiliently sothat the upper die clamp 11 is held on the head portion of the mountingnut 45. As a result, the upper die clamp 11 is supported in the rockingmanner.

[0043] Here, touching portions between the head portions of the mountingbolt 41 and the mounting nut 45 and the through holes 11H are formedinto a spherical contact surface so that the upper die clamps 11 rockssmoothly.

[0044] With reference also to FIG. 8, a locking projection 11P, whichfreely locks into a drop-proof groove 5G in the horizontal directionformed on the upper portion of the upper die 5, is formed on a lower endof the upper die clamp 11 so as to project towards the upper diesupporting section 9. A pressing member 47, which touches an inclinedplane 5S of the upper section 5U of the upper die 5 so as to press theupper die 5 against the upper die supporting section 9, is provided to aslightly upper portion of the locking projection 11P.

[0045] The pressing member 47 has a form obtained by working a part of aperipheral surface of a circular cylinder into a plane, and the pressingmember 47 is mounted to the lower portion of the upper die clamp 11 viaa plurality of screws 49 in a slightly rotatable manner.

[0046] Further, a wedge piece 51 (locking member) which is freelyengaged with the drop-proof groove 5G of the upper die 5 is provided onan upper portion of the locking projection 11P and between the pressingmember 47 and the locking projection 11P so as to freely advance andretreat. The wedge piece 51 is always biased so as to be engaged withthe drop-proof groove 5G by a function of a resilient member 53 such asa coil spring resiliently set between the wedge piece 51 and the upperdie clamp 11.

[0047] Movement of the wedge piece 51 by means of the biasing force isrestrained in such a manner that a part of the wedge piece 51 touches apart of the pressing member 47, and an inclined plane 51S is formed onan upper surface of an edge of the wedge piece 51 so that the wedgepiece 51 is easily engaged with and disengaged from the drop-proofgroove 5G.

[0048] With reference also to FIG. 3, the clamping force applying means13, which applies the clamping force for pressing and fixing the upperdie 5 to the upper die supporting section 9 using the pressing member 47provided on the lower portion of the upper die clamp 11 to the upper dieclamp 11, is included in a cylinder 55 in the front-rear directionprovided on the block section 7B of the holder body 7.

[0049] More specifically, the clamping force applying means 13 isconstituted so that both sides in the front-rear side of the cylinder 55are blocked by cover sections 55C, respectively, and two pistons 57 areprovided slidably to the front-rear direction in the cylinder 55. Apin-shaped pusher section 57P is projected to the outside of thecylinder 55 from the pistons 57, and the pusher sections 57P projectoutward from the through holes 55H provided on the cover sections 55C.Tips of the pusher sections 57P can touch and separate from a pressingscrew 59 as a pressure receiving member provided on the upper portion ofthe upper die clamp 11.

[0050] Further, a resilient member 61 such as a coil spring as a membercomposing a part of the clamp switching means 15 for biasing the piston57 to a direction where it is always pressed inward is wound around thepusher sections 57 of the pistons 57. Moreover, an oil passage 63 whichcommunicatively connects with the inside of the cylinder 55 between thetwo pistons 57 is formed on the block section 7B of the holder body 7,and the oil passage 63 is communicatively connected with a pressure oilsupply port 65 provided on a sidewall surface of the block section 7B.The pressure oil supply port 65 is communicatively connected with apressure oil supply source (not shown) via a hydraulic hose 67.

[0051] In a releasing state holding means 19 which freely holds theupper die clamp 11 in a state that the clamp of the upper die 5 isreleased, as shown in a cross section on the left side of FIG. 5, aspring support 69, which is engaged with a locking hole section 11Gformed on the upper portion of the upper die clamp 11 via a resilientmember 11S such as a spring, is fixed to the holder body 7, and theupper portion of the upper die clamp 11 is biased to a direction whereit is always pressed to the holder body 7 by the resilient member 11S.

[0052] The pressure receiving member which constitutes a main section ofthe mode of the present invention is detailed below.

[0053] With reference to FIG. 3, an elliptical notched portion 11C whichis long in the vertical direction (see FIGS. 6 and 7) is provided on aleft surface in FIG. 3 on the upper portion of the upper die clamp 11,for example, and a tapped hole 11N which pierces the notched portion 11Cis provided. The pressing screw 59 as the pressure receiving member isscrewed into the tapped hole 11N so as to freely advance and retreat,and a tip on the left side in FIG. 3 of the pressing screw 59 has apressure sensing surface 59P which is pressed by the pusher section 57Lof the piston 57.

[0054] A position lever shaft section 71 is screwed up to an end surfaceon the left side in FIG. 3 of the pressing screw 59 by a mounting bolt71B, and the position lever shaft section 71 can be rotated in thenotched portion 11C in a state that its outer peripheral surface isapproximately screwed into an upper semicircular side wall surface ofthe notched portion 11C. Moreover, a groove section 71G for a ring isprovided along the outer peripheral surface of the position lever shaftsection 71, and a stopper ring 73 for restraining rotation of theposition lever shaft section 71 to 180° is fitted into the groovesection 71G for ring. The stopper ring 73 has a shape such that itslower side in FIG. 7 expands outward from the groove section 71G forring. When the position lever shaft section 71 rotates by 180°, theexpanded portion of the stopper ring 73 touches the upper side wallsurface of the notched portion 11C so that the rotation is restrained.

[0055] A notched portion 71C for mounting a lever is provided on thelower side in FIGS. 3 and 6 of the position lever shaft section 71, anda position lever 75 which has a shape fitted into the notched portion71C is screwed up to the position lever shaft section 71. Moreover, amagnet 75M is buried in a right surface in FIG. 3 of the position lever75, and a spring pin 71P made of iron, for example, as a magneticmaterial which is attracted to the magnet 75M is buried in an area fromthe position lever shaft section 71 to the pressing screw 59.

[0056] With the above constitution, in the state of FIG. 3, when themagnet 75M is separated from the spring pin 71P and the position lever75 is lifted up so as to be rotated by 180°, also the position levershaft section 71 is rotated by 180°, thereby rotating also the pressingscrew 59. As a result, as shown in FIG. 4, the pressure sensing surface59P of the pressing screw 59 moves from a position represented by analternate long and short dash line to a position represented by a solidline. According to the rotation of the position lever shaft section 71,the expanded portion of the stopper ring 73 touches the upper sidewallsurface of the notched portion 11C so that the rotation by 180° isrestrained. When the position lever 75 is returned to its originalposition, the position lever 75 is attracted to the spring pin 71P viathe magnet 75M so as to be fixed to the position lever shaft section 71.

[0057] As mentioned above, selection is freely made from a first stagewhere the pressure sensing surface 59P of the pressing screw 59 isadvanced towards the pusher section 57P as shown in FIG. 3 and a secondstate where the pressure sensing surface 59P is retreated from the sideof the pusher section 57 as shown in FIG. 4 by rotating the positionlever 75 by 180°. That is to say, an opening quantity of the upper dieclamp 11 at the time of unclamping can be freely selected from the twostages.

[0058] In the above constitution, as the upper die 5 is shown by animaginary line in FIG. 5, when pressure oil is supplied into thecylinder 55 in the clamping force applying means 13 in a state that theupper die 5 is clamped between the upper die supporting section 9 of theholder body 7 and the upper die clamp 11, the pistons 57 advance outwardagainst the biasing force of the resilient member 61 and the tips of thepusher sections 57P touch the pressing screw 59 of the upper die clamp11, so that a pressing force (clamping force) of the cylinder 55 istransmitted thereto.

[0059] The upper die clamp 11 on the left side in FIG. 5 is movedrotationally to a counterclockwise direction and the upper die clamp 11on the right side in FIG. 5 is moved rotationally to a clockwisedirection by the pressing force (clamping force) of the cylinder 55, andthe upper die clamp 11 presses and fixes the upper die 5 more strongly.

[0060] On the contrary, when the pressure oil in the cylinder 55 isdischarged, the pistons 57 retreat inward due to the biasing force ofthe resilient member 61, and the tips of the pusher sections 57P move soas to separate from the pressing screw 59 of the upper die clamp 11 sothat pressing force (clamping force) of the cylinder 55 is released.

[0061] As shown in the cross section on the left side in FIG. 5,therefore, the upper portion of the upper die clamp 11 is moved to theholder body 7 by the resilient member 11S of the spring support 69, sothat the pressing screw 59 on the upper portion of the upper die clamp11 lightly touches the pusher sections 57P of the clamping forceapplying means 13, so that the pressing and fixing of the upper die 5 bythe upper die clamp 11 are released. The upper die 5 is supported so asto be movable to a longitudinal direction (horizontal direction) in astate that the locking projection 11P of the upper die clamp 11 isengaged with the drop-proof groove 5G.

[0062] In such a manner, since the upper die clamp 11 is easily operatedby the cylinder 55 (liquid pressure device), the upper die 5 is attachedto and detached from the holder body 7 efficiently.

[0063] That is to say, the lower portion of the upper die clamp 11 isopened so as to separate from the upper die supporting section 9, sothat the upper die 5 can be detached from the upper die clamp 11 so asto be replaced.

[0064] More specifically, at the first stage in FIG. 3, the openingquantity of the upper die clamp 11 at the time of unclamping becomessmaller than that at the second stage in FIG. 4 because the position ofthe pressure sensing surface 59P of the pressing screw 59 advances. Theengaged state between the wedge piece 51 and the drop-proof groove 5G ofthe upper die 5 at this time is such that even if the upper die 5 istried to be drawn downward against the biasing force of the resilientmember 53 to the direction of the upper die supporting section 9 of thewedge piece 51, the tip of the wedge piece 51 projects further than theengaging projection 112 at the lower end of the upper die clamp 11,thereby preventing the upper die 5 from being drawn. So to speak, theupper die 5 cannot be front-fed and front-removed. The upper die 5 canbe, however, drawn to the lateral direction.

[0065] Further, when the position lever 75 is rotated by 180° so as tobe at the second state in FIG. 4, the position of the pressure sensingsurface 59P of the pressing screw 59 retreats, so that the openingquantity of the upper die clamp 11 at the time of unclamping is largerthan that at the first stage in FIG. 3. The engaged state of the wedgepiece 51 with the drop-proof groove 5G at this time is such that theupper die 5 can be drawn downward against the biasing force of theresilient member 53 towards the upper die supporting section 9 of thewedge piece 51. That is to say, the tip of the wedge piece 51 retreatsfurther than the locking projection 11P at the lower end of the upperdie clamp 11, so that the upper die 5 can be drawn downward. Moreover,on the contrary, the upper section 5U of the upper die 5 can be insertedbetween the upper die supporting section 9 of the holder body 7 and theupper die clamp 11 from a lower direction. So to speak, the upper die 5can be front-fed and front-removed.

[0066] According to the above constitution, even if the upper die 5 isslid mightily and thus a stronger force than the biasing force of theresilient member 53 of the wedge piece 51 is applied to the upper die 5at the time of replacing, the position levers 75 can be switched intothe first stage, so that a danger such that the upper die 5 drops evennot at the time of first-feeding and first-removal is eliminatedcompletely. Moreover, the position lever 75 is switched into the secondstage, so that the upper die 5 can be easily front-fed andfront-removed.

[0067] By the way, in this mode, since a stroke of the cylinder 55 isabout 3 mm, a mechanism having two-stage stroke can not be incorporatedinto the cylinder 55, and there is generally a limit in incorporating ofthe cylinder 55 with large stroke due to a thickness of the holder body7. Moreover, since the 6 to 30 upper die holder apparatuses 1 areattached to the press brake, the clamping force of the cylinder 55differs according to individual difference between the upper die holderapparatuses 1, and thus an accurate operation cannot desired.

[0068] In this mode, however, the two-stage unclamping operation can beperformed securely only by a simple operation for rotating the positionlever 75 by 180°. Since the press brake has a plurality of the upper dieholder apparatuses 1, the simplicity of the switching operation isgreatly effective from a viewpoint of operability.

[0069] The present invention is not limited to the examples of the mode,and another modes can be carried out by making suitable modifications.

1. An upper die holder apparatus comprising: a holder body; an upper diesupporting section provided to a lower portion of the holder body, theupper die supporting section for supporting an upper die; an upper dieclamp supported to the holder body in a rocking manner, the upper dieclamp being supported in a rocking manner with a vicinity of a center ina vertical direction of the holder body being as a supporting point; apressing member provided to a lower portion of the upper die clamp, thepressing member for pressing the upper die against the upper diesupporting section; a locking member provided to a lower portion of theupper die clamp, the locking member being biased towards the upper diesupporting section so as to freely lock into a drop-proof grooveprovided to the upper die; clamping force applying means provided to theholder body, the clamping force applying means pressing an upper portionof the upper die clamp so that the upper die clamp clamps the upper die;and a pressure receiving member provided to an upper portion of theupper die clamp, the pressure receiving member having a pressure sensingsurface to be pressed by the clamping force applying means, wherein thepressure receiving member is provided so that its advancing andretreating are adjusted to a pressing direction by the clamping forceapplying means; and wherein the pressure receiving member is provided sothat an opening quantity of the upper die clamp at the time ofunclamping is freely selected between a plurality of stages.
 2. Theupper die holder apparatus according to claim 1, wherein the openingquantity of the upper die clamp at the time of unclamping is adjustableso that a locked state between the locking member and the drop-proofgroove of the upper die is freely selected from a first stage where theupper die cannot be drawn downward and a second stage where the upperdie can be drawn downward.
 3. The upper die holder apparatus accordingto claim 2, wherein the pressure receiving member is screwed into theupper portion of the upper die clamp; and wherein a position lever whichis rotated so as to advance and retreat the pressure receiving membergradationally is provided to the pressure receiving member.